Silver halide emulsions containing a diamino diphenyl amine stabilizer



SILVER HALIDE EMULSIONS CONTAINING A DI- AMINO DIPHENYL AMINE STABILIZERClinton S. Ballard and Wesley G. Lowe, Rochester, N. Y., assignors toEastman Kodak Company, Rochester, N. Y., a corporation of New Jersey NoDrawing. Application December 31, 1953, SerialNo. 401,718

5 Claims. (Cl. 95-7) Our invention relates to the stabilization of lightsensitive silver bromide emulsions such as silver bromidegelatinemulsions.

It is known that silver bromide emulsions such as are used to sensitizephotographic papers lose their sensitivity upon storage of thephotographic paper sensitized therewith.

One object of our invention is to provide emulsions which retain theirsensitivity much more effectively when photographic products sensitizedby said emulsions are stored. Other objects of our invention will appearherein.

We have found that the stability of silver bromide emulsion layers ismarkedly improved if there is incorporated into the emulsion, prior tothe coating therewith of a support, an ortho or paradiaminodiphenyldisulfide or its salt or an ortho or para diaminodiphenylamine or its salt. The stabilization of the emulsion is effective witheither the unsubstituted compounds or with compounds in which dimethylor diethyl amino groups are used. Some of the compounds which have beenfound to be useful for stabilizing silver bromide emulsions inaccordancewith our invention are 4,4-diaminodiphenyldisulfide dihydrochloride,2,2'-diaminodiphenyldisulfide, 4,4'-diaminodiphenyl amine sulfate,4,4'-dimethylamino diphenylamine hydrochloride, and the like. We havefound that various proportions of the amines or disulfides as specifiedare useful for stabilizing silver bromide emulsions but that moreeffective results are obtained if the amount of the compound added tothe emulsion is equivalent to at least 2 mg. per mole of silver halide.The proportion of 232 mg. of the disulfide or amine per mole of silverhalide has been found to be the most successful. Those disulfides whichappear to be most useful in accordance with our invention are thosehaving the formula as follows:

R R R R where the amino groups are either ortho or para to the sulfidesubstituent, R being selected from the group consisting of hydrogen,methyl and ethyl. In the above formula either R may be the same in anyone compound, some of the Rs may be different than the others or the Rsmay all represent different substituents. As for the nited States Patent2,756,145 Patented July 24, 1956 2 amines which are useful the followingstructural formula illustrates compounds which may be employed:

where R may be either hydrogen, methyl or ethyl; R may be either all thesame or some may be hydrogen and others may be methyl or ethyl groups.If desired these compounds may be employed in the form of their saltssuch as the hydrochloride or the sulfate. The amount of the additiveemployed in the silver bromide emulsion may be any amount thereof from 2up to 32 mg. per mole of silver halide in the emulsion. The emulsionswhich are stabilized in accordance with our invention are characterizedby the use of silver bromide as the principal sensitizing material butthere may be cases where some other silver halide may be employed.Although our invention is primarily directed to the stabilizing ofgelatin photographic emulsions, we are also aware that there may be someother suspending material substituted at least in part for the gelatinof the photo graphic composition. The carrying material for the silverbromide may be polyvinyl alcohol, may be a modified protein as describedin Lowe and Gates Patent No.

2,691,582 issued October 12, 1954, or some other protein material, ormay be a synthetic polymer material, or it may be a mixture of gelatinwith some other protein material or a polymeric hydrosol such asdisclosed in application Serial No. 272,709 of Fowler or in theapplications relating to polymers prepared from protein derivatives andtheir mixtures with gelatin, in the names of Fowler and Gates and Gates,Illingsworth and Dann, Serial Nos. 398,234 and 398,236 respectively,filed December 14, 1953.

The following examples illustrate our invention:

EXAMPLE 1 A silver bromoidide emulsion containing 1.3 mol percent silveriodide was divided into several fractions and to each fraction was added4,4-diaminodiphenyldisulfide dihydrochloride in various proportions from2 to 32 mgs. per mole of silver halide. Each smulsion fraction wasapplied as a thin layer on to baryta coated paper base. A sample of eachcoating was used for preparing a paper test strip. Each test strip wasthen exposed on a sensitometer and developed for one minute inphotographic developer, D-72, diluted 1:1. The strips were then read ona densitome'ter and contrast measurements were made to determine thevalue of log ES obtained in the manner described. This value indicatesthe change in contrast of the paper over a period of time. The largerthe degree of difference as indicated by log ES the greater the amountof breakdown which has occurred. (See page 189 of Fundamentals ofPhotographic T heoryJames and Higgins.)

After the above procedure the test strips were read on a densitometerand contrast measurements were made as described. The value of log ESwas obtained in accordance with the method specified by the AmericanStandardbetween the log ES values of incubated and fresh strips.

Table I Mg. Fresh Incub A Log ES Log ES Log ES EXAMPLE 2 A silverbromide emulsion having difierent sensitornetric characteristics thanthat of the emulsion employed in the previous example was divided intoseveral fractions.

ner described in the previous example. The values given show the changein log ES as a result of the incubation:

Added stabilizer: A log ES 2,2-diaminodiphenyldisulfide .004,4-diaminodiphenylamine sulfate 4,4'-dimethylamino diphenylaminehydrochloride 2,2'-dimethylamino diphenyl disulfide 'We claim: I

1. A silver halide photosensitive emulsion stabilized againstdeterioration by aging, which emulsion contains 2-32 mgs. per mole ofsilver halide of a compound selected from the group consisting of thediaminodiphenyl amines having the structural formula:

the R substituent being selected from the group consisting of hydrogen,methyl, and ethyl, and the mineral salts thereof.

2. A silver bromide photosensitive emulsion stabilized againstdeterioration by ageing which emulsion contains 2-32 mgs. per mole ofsilver halide of a diarninodiphenyl amine.

3. A silver bromide photosensitive emulsion stabilized againstdeterioration by ageing which emulsion contains 2-32 mgs. per mole afsilver halide of a diaminodiphenyl amine salt.

4. A photosensitive silver bromide emulsion which emulsion is stabilizedagainst deterioration due to ageing by a content of 2-32 mgs., per moleof silver halide, of 4,4-dimethylaminodiphenyl amine hydrochloride.

5. A photosensitive silver bromide emulsion which emulsion is stabilizedagainst deterioration due to ageing by a content of 2-32 mgs. per moleof silver halide of 4,4-diaminodiphenyl amine sulfate.

References Cited in the file of this patent UNITED STATES PATENTS

1. A SILVER HALIDE PHOTOSENSITIVE EMULSION CONTAINS AGAINSTDETERIORATION BY AGING, WHICH EMULSION CONTAINS 2-32 MGS. PER MOLE OFSILVER HALIDE OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OFDIAMINODIPHENYL AMINES HAVING THE STRUCTURAL FORMULA: